Hitless Line Switching in 1:1 Protection Transmission Systems
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Solution Overview
Problem
In 1:1 protection schemes, packet loss or sequence changes occur due to delay differences between communication lines, making preventive maintenance line switching impossible.
Innovation Solution
A transmission system that performs line switching based on error correction status without causing packet loss or sequence changes, using error-correction coding and buffer management to ensure seamless switching during error compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If line switching is performed in 1:1 protection scheme, then communication reliability is improved, but packet loss or sequence changes occur due to delay differences between lines
Solution Approach 1:
The patent applies preliminary action by performing error-correction coding on packets before transmission. The transmission device encodes packets with forward error correction (FEC) codes in advance, so that even if packets are lost or corrupted during transmission due to line switching, the reception device can recover the original packets using the embedded error correction information, thereby preventing packet loss.
Solution Approach 2:
The patent implements beforehand cushioning by introducing buffering mechanisms at the reception device. Buffers are used to temporarily store received packets and allow for reordering and recovery operations. This cushioning mechanism absorbs the impact of delay differences and packet losses during line switching, ensuring continuous and accurate packet delivery.
2Reliability
If line switching is performed in 1:1 protection scheme, then communication reliability is improved, but sequence changes occur due to delay differences between lines
Solution Approach 1:
The patent applies feedback by implementing sequence number tracking and packet reordering mechanisms. The reception device monitors packet sequence numbers, detects out-of-order arrivals caused by line switching, and uses feedback loops to reorder packets correctly before forwarding them to the upper layer, thereby maintaining packet sequence stability despite line switching operations.
Solution Approach 2:
The patent uses preliminary action by pre-numbering packets with sequence identifiers before transmission. This allows the reception device to identify and reorder packets that arrive out of sequence due to different transmission delays on alternative lines, ensuring correct packet sequencing is restored after line switching.
3Reliability
If error-correction coding is applied during line switching, then packet loss is prevented, but processing complexity increases
Solution Approach 1:
The patent applies parameter changes by selecting different FEC code rates and buffer sizes based on network conditions and line characteristics. By adjusting these parameters, the system optimizes the balance between error correction capability and processing complexity, achieving reliable packet delivery without excessive computational overhead.
Solution Approach 2:
The patent uses disposable error correction codes that are computed once per packet and discarded after use, rather than maintaining complex persistent correction mechanisms. This approach provides effective error correction with minimal ongoing processing complexity, as each packet carries its own self-contained error correction information.
Data Source
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AI summary
When a first communication device receives a predetermined message from a second communication device via a third line in a state of transmitting frames to a first line while performing error-correction coding on the frames, the first communication device switches the line to a second line after transmitting a frame of a post-switching message to the first line, and continues transmission. The second communication device receives the frames from the first and second lines and performs error correction, stores the frames, on which error correction has been performed, in first and second buffer, and when determining that it is necessary to perform line switching based on the status of error correction with respect to the frames received from the first line, transmits a predetermined message to the third line, and when receiving the frame of the post-switching message from the first line, starts reading of the frames from the second buffer after reading all of the frames stored in the first buffer.